1. Field of the Invention
This invention relates to biosensors, and in particular, articles containing a plurality of biosensors suitable for use with an apparatus, e.g., an analyte meter, for determining the presence or concentration of analytes in a biological sample.
2. Discussion of the Art
The prevalence of diabetes has been increasing markedly in the world. At this time, diagnosed diabetics represent about 3% of the population of the United States. It is believed that the total actual number of diabetics in the United States is over 16,000,000. Diabetes can lead to numerous complications, such as, for example, retinopathy, nephropathy, and neuropathy.
The most important factor for reducing diabetes-associated complications is the maintenance of an appropriate level of glucose in the blood stream. The maintenance of the appropriate level of glucose in the blood stream may prevent and even reverse many of the effects of diabetes.
Glucose monitoring devices of the prior art have operated on the principle of taking blood from an individual by a variety of methods, such as by needle or lancet. The individual then coats a paper strip carrying chemistry with the blood, and finally inserts the blood-coated strip into a blood glucose meter for measurement of glucose concentration by determination of change in reflectance.
The medical apparatus of the prior art for monitoring the level of glucose in the blood stream required that an individual have separately available a needle or lancet for collecting blood from the individual, strips carrying blood chemistry for creating a chemical reaction with respect to the glucose in the blood stream and changing color, and a blood glucose meter for reading the change in color indicating the level of glucose in the blood stream. The level of blood glucose, when measured by a glucose meter, is read from a strip carrying the blood chemistry through the well-known process of reading reflectometers for glucose oxidation.
The prior art discloses numerous electrochemical and optical biosensors, e.g., test strips, for measuring the concentration of an analyte in a test sample. In particular, the art discloses disposable test strips for the measurement of glucose level in whole blood that deal primarily with the reaction layer used to generate an analytical response, the mode of measurement, and the algorithms used in the measurement.
Electrochemical assays for determining the concentrations of enzymes or their substrates in complex mixtures of liquids have been developed. Test strips (i.e., biosensors in the form of test strips) are useful in external testing. In external testing, test strips can function in a non-invasive manner (i.e., as strips that come into contact with blood withdrawn by a syringe or a lancing device). In particular, test strips for biomedical applications (e.g., whole blood analyses) have been developed for the determination of glucose levels in biological samples. In general, test strips comprise electrochemical cells in which there can be working electrodes, counter electrodes, and reference electrodes. The potential of the working electrode is maintained at a constant value relative to that of the reference electrode.
A minimally painful technique for obtaining body fluids is described in U.S. Pat. No. 6,063,039. This patent discloses an apparatus for obtaining blood for diagnostic tests. The apparatus comprises a housing having a sealable chamber located therein and a sealable opening in fluid communication with the sealable chamber, a power source, a vacuum pump operably connected to the power source, the vacuum pump in communication with the sealable chamber, a lancing assembly positioned within the sealable chamber, and a fluid collector (biosensor in the form of a test strip) positioned in the sealable chamber, the fluid collector in fluid communication with the sealable opening. However, only one fluid collector can be positioned in the housing of the apparatus at a time. The user must manually remove a consumed fluid collector from the housing, before another fluid collector can be inserted therein. It would be desirable to improve that system in order to allow more than one fluid collector to be inserted into the housing at a time, in order to simplify the use of the apparatus for the user.
Osaka et al., U.S. Pat. No. 5,228,972, discloses an apparatus for measuring concentration of test substances in liquid. The apparatus comprises one or more thin plates having one or more openings through which a test substance to be measured is penetrated, in a predetermined position thereof, diffusion-limiting membranes for limiting diffusion of the test substance adhered to the thin plates for covering the openings, a casing for housing the one or more thin plates, and a driving mechanism for moving the thin plate by a predetermined distance. The thin plate may be disk-shaped, strip-shaped, or elongated. The elongated thin plate may further be rolled. The casing is provided with the driving mechanism and is positioned in a test apparatus body having a concentration-measuring electrode therein. Multiple measurements of concentration of a test substance are carried out by moving the thin plate by the driving mechanism to position the diffusion-limiting membrane having the test solution deposited thereon to the position available to contact with the concentration measuring electrode, while keeping the casing placed in the test apparatus body. However, U.S. Pat. No. 5,228,972 requires a casing and a diffusion-limiting membrane. Moreover, the thin plate must be moved by the driving mechanism to position the diffusion-limiting membrane having the test solution deposited thereon to a position available to contact the concentration-measuring electrode, while keeping the casing placed in the test apparatus body.
Nozoe et al., U.S. Pat. No. 5,741,634, discloses a disk-shaped sensor body containing a plurality of elemental sensors radially extended outward from the circumference thereof. The sensor body is made from an insulating material. The circumferential portion of the sensor body is shaped to have v-shaped notches equidistantly and angularly arrayed therearound. Of these notches, the adjacent notches define a trapezoidal part. The notches and trapezoidal parts are alternately arrayed on the circumference of the sensor body. The sensor elements are formed in the trapezoidal parts. In the sensor circuit, a sensor portion is formed of a counter electrode, a reference electrode, a first working electrode, and a second working electrode. Additional films are positioned over the two working electrodes. However, U.S. Pat. No. 5,741,634 does not provide a means for integrating the measurement function with the sample extraction function and sample transfer function.
The foregoing patents describe several ways to package a plurality of test strips for determining the concentration of analytes. However, neither of these patents disclose a device wherein a device for collection of biological samples and storage of a plurality of biosensors are integrated into a single entity. “Ascensia Breeze” test strips (Bayer) and “Accu-Chek Compact” test strips (Roche) involve packaging a plurality of individual test strips in sealed chambers and indexing unused test strips into position for measuring the concentration of glucose. However, these test strips require complicated advancing and indexing mechanisms to pierce sealed chambers, to advance and index the test strips into position for testing, and to eject used test strips after testing.